1. Field of the Invention
The present invention relates to an image forming apparatus including a laser printer.
2. Description of the Related Art
An image forming apparatus including photoreceptors arranged in parallel for their respective colors of yellow, magenta, cyan, and black, is generally known as a tandem image forming apparatus. The tandem image forming apparatus is provided with developing rollers for supplying the corresponding color toners to their respective photoreceptors. The color toners are supplied from the developing rollers to the photoreceptors, respectively, to form color toner images on surfaces of the photoreceptors substantially simultaneously. Then, the toner images of the respective colors on the surfaces of the photoreceptors are transferred directly to the paper so that the toner of the respective colors are superposed on the paper, thereby accomplishing the formation of a color image on the paper. Alternatively, the toner images of the respective colors are transferred to an intermediate transfer belt so that the toner of the respective colors are superposed on the intermediate transfer belt, first, and, then, the resultant color image is transferred to the paper, thereby accomplishing the formation of a color image on the paper.
A tandem image forming apparatus comprising cartridges having developing rollers, respectively, elastic members for biasing the cartridges in a direction of the developing rollers being pressed to photoreceptor belts, and detaching cams rotatably supported on rotating shafts extending in axial direction of the developing rollers is proposed as an example of such a tandem image forming apparatus (cf. Japanese Unexamined Patent Publication No, 2002-6716, for example). This image forming apparatus is structured so that when the detaching cams are brought into contact with supporting shafts of the developing rollers by the rotation of the detaching cams, the developing rollers are detached from the photoreceptor belts against biasing force of the elastic members. When the detaching cams are detached from the supporting shafts of the developing rollers, the developing rollers are pressed on the photoreceptor belts by the biasing force of the elastic members.